Liquid handling member with inner materials having good creep recovery and high expansion factor

ABSTRACT

The present invention is a deformable liquid handling member, having an inner region circumscribed and hermetically sealed by a wall region, which comprises a membrane assembly to separate a first zone outside of the member from a second zone within the inner region of the member. Thereby, the second zone is connected to a suction source capable of receiving liquid, and the first zone is positioned in liquid communication with a liquid releasing source during its intended use. The membrane assembly is capable of maintaining a pressure differential between the second zone and the first zone without permitting air to penetrate from said first zone to said second zone. Further, the inner region comprises an inner material, which has a volume expansion factor of more than 3, preferably 5, more preferably 10, and can have a creep recovery of more than 60%, preferably more than 90%.

BACKGROUND/PRIOR ART

Liquid handling systems comprising a membrane are known in the art. Forexample, U.S. Pat. No. 5,678,564 discloses a liquid removal systemdesigned to permit liquid removal through the use of an interfacedevice. The interface device is provided with a membrane which has andis capable of maintaining a vacuum on one side so that when liquidcontacts the opposite side of the membrane the liquid passes through themembrane and is removed from the interface device by a maintained vacuumto a receptacle for disposal. Such a system is described to be useful asa female external catheter system. Also, in PCT application US99/14654various desired properties for materials inside such interface devicesare described, with particular embodiments showing collapsible innermaterials.

Yet, there is a need for materials exhibiting improved properties withregard to maximizing the functionality especially over longer storageand/or use periods

Thus the present invention aims at providing liquid handling membercomprising inner materials with good creep recovery, low minimum liquidloading whilst maintaining functionality, and high maximum loadingwhilst maintaining functionality.

SUMMARY

The present invention is a deformable liquid handling member, having ainner region circumscribed and hermetically sealed by a wall region,which comprises a membrane assembly to separate a first zone outside ofthe member from a second zone within the inner region of the member.Thereby, the second zone is connected to a suction source capable ofreceiving liquid, and the first zone is positioned in liquidcommunication with a liquid releasing source during its intended use.The membrane assembly is capable of maintaining a pressure differentialbetween the second zone and the first zone without permitting air topenetrate from said first zone to said second zone. Further, the innerregion comprises an inner material, which has a volume expansion factorof more than 3, preferably 5, more preferably 10, and a creep recoveryof more than 60%, preferably more than 90%.

Preferably, the inner material has an net uptake value of more than 6.5g/g in the horizontal Surge Capacity test, and more than 5.5 g/g in thevertical Surge Capacity test. The inner material further comprises acreep resistant material having an elastic modulus of at least 10 MPa,an elongation at break of at least 60%, compression set less than 25%,and can maintain these values after accelerated aging for 3 days at 60°C.

A liquid handling member according to the present invention can beconstructed by using repeating geometric units, which can be positionedbetween a first and a second support layer, arranged in an essentiallyparallel configuration extending in x-/y-direction perpendicular totheir thickness along the z-direction at a distance H to each other, anda spacer layer having a material thickness significantly smaller thanits x-/y extension, which is arranged and attached in a non-parallelorientation to and between said support layers, whereby the distance Hof said support is greater than the thickness b of the spacer layer.

In a particular embodiment, the present invention comprises amultiplicity of spacer layers.

In a particular embodiment, the present invention comprises an innermaterial with a spacer layer arranged in corrugations, pleats, folds,walls, tubes, spheres, semishperes, which can be continuous or not.

The inner material spacer layer is preferably made of elastomericmaterials, such as vulcanized polyurethane, and chemically cross-linkedrubber, preferably SBR or Isoprene rubber or natural rubber, and theinner material support layer materials can be woven or nonwoven such asmade from Nylon, or apertured films..

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A is a schematic representation of suitable materials.

FIG. 1B is another embodiment of the present invention.

FIG. 1C is a cross sectional view showing a liquid handling memberconstructed in accordance with the present invention.

FIG. 1D is a cross sectional view showing another embodiment of a liquidhandling member constructed in accordance with the present invention.

FIG. 2 shows the sample holder for the bulk softness test.

DETAILED DESCRIPTION

In the context of the present invention, a “liquid handling member” isconsidered to be a device, wherein a liquid is penetrating through amembrane by a driving force such as a suction like a vacuum. If thismember is connected to a liquid delivery source, or liquid receivingsink, thus forming a “liquid handling system”, this can be used inapplications such as for—but without being limited to—receiving bodyliquids. In such applications, the liquid to be transported will begenerally water based, such as body liquids like urine. It will beapparent to the skilled person, that the present invention is notlimited to such applications, but that it can be readily re-applied toother liquids such as oily substances as disclosed in PCT applicationsUS 99/14644 or US 99/14645.

As shown in FIG. 1C, a deformable liquid handling member 100,constructed in accordance with the present invention, has an innerregion 120 circumscribed and hermetically sealed by a wall region 110,which comprises a membrane assembly 112 to separate a first zone 135outside of the member 100 from a second zone 125 within the inner region120 of the member 100. The second zone 125 is in liquid communicationwith a suction source 130 capable of receiving liquid, and the firstzone 135 is positioned in liquid communication with a liquid releasingsource 140 during its intended use. The membrane assembly 112 is capableof maintaining a pressure differential between the second zone 125 andthe first zone 135 without permitting air to penetrate from said firstzone 135 to said second zone 125. Further, the inner region 120comprises an inner material 122, which has a volume expansion factor ofmore than 3, preferably 5, more preferably 10, and a creep recovery ofmore than 60%, preferably more than 90%.

Such systems function by the principle that certain membranes undercertain conditions can be permeable to liquids, but not to gases likeair, as long as the “potential differential” such as the pressuredifferential between the two sides of such a membrane does not exceed acertain value, which is characteristic for a given material and givenliquid in the pores of the material—the “bubble point pressure”. Thislatter is often expressed in “height of water column” which correspondsto the pressure exerted by such a column on the material under normalgravity conditions.

For aqueous liquids, the material for the membrane is preferablyhydrophilic and has a pore size of a diameter of about 5 to about 30 μm,more preferably about 10 to 20 μm. Once the membrane has been wetted itwill support a suction pressure typically corresponding to about 12.5 cmto about 150 cm height of a water column without permitting air to passtherethrough. Thus, if suction is applied to one side of a wettedmembrane, liquid contacting the membrane on the other side will be drawnby the suction through the membrane to the other side of the membrane,from where it can further be removed, for example by being sucked bymeans of a vacuum through a drain tube to a reservoir. As long as thefilter material or membrane remains wet, air does not pass through thefilter and suction is maintained without active pumping. If too muchsuction (too high vacuum) is applied to the membrane, there is a riskthat the bubble point of the membrane will be surpassed and there willbe no liquid in one or more pores of the membrane, thereby allowing airor gas to penetrate through, which can lead to a loss of the vacuum, andof the liquid handling functionality. Thus the amount of vacuum shouldapproach as close as possible—but not exceed—the bubble point.

In such a system, the membrane needs to be “hermetically sealed” to theother elements, which means that a gas (and especially air) can neitherpass from the outside environment to the inside of the member, when themembrane is saturated with liquid, as long as the pressure differentialdoes not exceed the bubble point pressure.

This hermetic sealing can be achieved by only using membrane materials,and appropriately sealing them to each other to close the system. Inaddition to the membrane materials, there may be used liquid and vaporimpermeable walls, such as for sealing areas where no membranefunctionality is required or desired. Then, the membranes must also be“hermetically” connected to these wall regions.

The membrane of the member needs to maintain a certain degree ofwetness, so as to maintain the pores filled with liquid, even -undersuction vacuum, and/or evaporation conditions. As described for examplein U.S. Pat. No. 5,678,564, the membrane material can be prewettedduring manufacture. This may be done by any suitable liquid havingpreferably a low vapor pressure. Glycerin has been proposed as aprewetting agent because it has a significant smaller propensity fordrying out by evaporation and will generally support the vacuum untilthe first wetting during use.

Generally, such systems can exhibit relatively high liquid transportrates. Thereby, it has been found useful to consider liquid “flux”through the system, expressed in flow of liquid per unit area of thesystem, e.g. [ml/sec/m²]

In particular for applications where a low bulk is desired or requiredbefore its intended use (i.e. after manufacturing, and during shipmentand storage, or in case of absorbent articles, such as externalcatheters, during wear time but before or after the loading phase), thematerials in the inner regions are preferred to be compressible orcollapsible during this phase so as to provide small volume andpreferably also low weight, and to be expandable during the actualliquid handling step.

Similarly, it further can be advantageous, if the liquid handling membernot only provides a high flux transport functionality, but that it has acertain buffer capacity. For example, if the total liquid handlingsystem comprises a liquid storage member which has a relatively slowrate for receiving liquids, the liquid handling member can quicklyreceive gush volumes, and temporarily store these to release the liquidat a slower rate to the liquid storage member.

Henceforth, it can be very beneficial to have liquid handling memberswhich are deformable. This has to be seen in the context of the intendedapplication, i.e. these members should be able to adopt their overallshape to or during in-use conditions. In particular, when such membersare applied for hygiene articles, they should conform to the bodycontours under normal forces as occurring during use. This is consideredto be an important advantage over members having stiff elements, such asmay be required to withstand deformation forces as can result fromapplying a vacuum suction to the member, such as described in U.S. Pat.No. 5,678,564.

A deformable member can be and preferably is deformable in its thicknessdimension as described in further detail by having collapsible orexpandable materials encased by a flexible casing. A deformable membercan be and preferably is bendable in the x- and/or y-direction, i.e.perpendicular to its thickness direction.

Whilst it will be apparent to the skilled person to distinguish stiffstructures, such as the shells as described in the already mentionedU.S. Pat. No. 5,678,564, deformable structures can be assessed by thebending test, as described in the test method section, preferablyexhibiting buckling force values of less than 1 N, preferably less than5 N, and more preferably less than 3 N or even less than 1 N.

Materials useful for application as inner materials of a liquidtransport member in general have been described in PCT applications US98/13497, generally exhibiting a high porosity and permeability.Therein, fibrous members are described using high-loft non-wovens, e.g.,made from polyolefin or polyester fibers. Other suitable materialsdescribed therein are porous, open celled foam structures, such aspolyurethane reticulated foams, cellulose sponges, or open cell foams asmade by the High Internal Phase Emulsion Polymerization process (HIPEfoams).

Alternatively, suitable properties could be achieved by circumscribingvoids by certain structures, such pipes, or bundles, or by other “spaceholders”, such as springs, spacer, particulate material, corrugatedstructures and the like.

Such materials have the ability to be compressed during transport fromthe manufacturing site to the user in a relatively thin (or low-volume)state, and upon application such materials can be activated, such asupon contact with the source liquid, to increase their volume so as tosatisfy the void and permeability requirements.

Thus, one important property of such materials is their minimum liquidloading capacity, i.e. the minimal amount of liquid, which has to beretained in these members without losing their membrane and liquidtransport property. The lower this value is, the less material needs tobe transported.

At the same time, it is important, that the materials useful in suchapplication have the ability to receive large amounts of liquid, i.e.have a high maximum loading capacity. Such a high capacity is not onlybeneficial for the interim storage aspect, but also indicates arelatively open structure, which is linked to the permeability of thematerial within the member.

This maximum loading capacity can be somewhat different according to themechanism of loading, for example, for horizontal loading versusvertical loading, and as reflected in respective testing arrangementsfor the horizontal and vertical surge capacity, as describedhereinafter.

Thus, the minimum loading capacity and the maximum surge capacity valuesdetermine the maximum net uptake, i.e. the maximum amount of fluid, asthe difference between the two values.

When basing this net uptake capacity on the amount of material, theexpansion factor can be determined. For aqueous liquids with a densityof about 1.0, this expansion factor can be expressed as volumetricexpansion factor (VEF), which also corresponds to the volume increase ofthe member upon activation. Thus, the VEF for a fully wetted strucure isthe value of the volume of the liquid in the expanded state divided bythe volume of the liquid in the compressed state.

It has now been found, that with an increase in expansion factors alsothe mechanical stress to which the materials are exposed, insignificantly increasing, and that materials can lose their ability toregain their original volume if exposed to such compression forces foran extended period.

An extended period can be as short as several hours, but—for examplewhen considering shipment and storage of manufactured articles, beforethese reach the user—can be several months.

A simple way to express creep is to measure the ability of a material tore-gain its caliper, after being submitted to compressive forces, suchas a load or pressure applied to the material, for an extended period oftime.

Creep can be measured on TA Instruments' (New Castle, Del., US) DynamicMechanical Analyzer, DMA 2980. In this test, a constant compressivestress is applied to the sample and the resulting strain is measured asa function of time. After a set time, the stress is removed and thestrain (recovered caliper) is measured a s a function of time.

Coinciding with deformation of the material, an impact of pore size andporosity with the compression aging can be observed, such that theporosity can be reduced, and/or average pore size, and/or permeabilityof the material.

Particularly suitable materials exhibit a high ratio of porosity whenexpanded compared to collapsed or compressed. Whilst for exampleconventional polyurethane foams exhibit a porosity of 95% or more whenbeing uncompressed, this is reduced to about 85% such as when exposed toa pressure of about 8950 Pa (about 1.3 psi). Preferred structures asdescribed hereinafter, can be compressed to a porosity of less than 50%,more preferred ones to less than about 30% when exposed to a pressure ofabout 8950 Pa (about 1.3 psi), even when exhibiting a porosity of 90% oreven 80% without applied pressure.

Henceforth, the materials suitable for being used in the presentinvention need to have carefully balanced properties with regard to theones as described above.

For example, conventional PU foams, such as exemplified in the PCTapplication US 98/13497 do not meet the creep requirements, and furtherexhibit too high minimal loading values, and consequently too low volumeexpansion factors.

Materials suitable for the present application have the followingproperties, as can be evaluated by the respective test as describedhereinafter: First, a net uptake value of at least 5 g/g, preferably atleast 7 g/g, more preferably more than 10 g/g; second, a volumeexpansion factor of at least 3, preferably at least 5, more preferablymore than 10; and thirdly a creep recovery value of at least 60%,preferably 90% even more preferably more than 95% after 22 hours agingunder 8950 Pa (1.3 psi).

For applications in the hygiene field, such as for absorbent articles,it is preferred, that the material has an initial wet weight for 75 mlgush loading of less than 80 g, preferably less the 50 g, even morepreferably less than 40 g.

Whilst the materials useful for the present invention can be made fromvarious structures, it has been found that particularly useful materialscan be constructed as “organized structures”—with repeating geometriccells.

The term “organized structures” relates to material composites, whichcombine materials in particularly effective designs, which will providesignificantly different properties than the “precursor” materials alone.A well known example for such structures is the corrugated cardboard ,where relatively thin and flexible paper sheets are combined into a muchmore rigid structure. The principles of such structures are exploitedfor the present invention, whereby, however, particular considerationhas to be given to particular properties and parameters.

A particularly preferred execution uses repeating geometric units, whichcan have two dimensional repeating cell units (as the repeatingcross-sections for corrugations, pleats or folds), or can havethree-dimensional repeating cell units (such as for having a sheetmaterial with protuberances extending from both surfaces, such as resultfrom particular embossing).

Such repeating geometric cells can have smooth transitions from one cellto the next—such as the well-known card-board corrugations.Alternatively, there can be certain discontinuities between adjacentcells, such as when there are folds or in the connection sections. Also,if the structure consists of several materials, not all of these need tobe present throughout the structure, but can be restricted to certainparts of the structure.

For ease of explanation, the following explanation will considercorrugated structures, but this should not be considered in any way as alimiting embodiment. For such idealistic structures, it is assumed, thatthe geometric unit cell consists of two horizontal support layersconnected and spaced apart by vertical walls. For non-ideal pleated orcorrugated structures, these vertical walls can be inclined, can contactneighboring walls (such as forming a V or M or a “Leporello” structure)or can be rounded such as like connecting semi-circular elements, orhaving sinusoidal shape. Also, the inner materials can be in the form oftubes, spheres, semi-spheres, etc. as long as there is provision forliquid to transfer easily through such structures, such as by keepingthe ends of pipes open, or having apertures in the walls of spheres.

For all of these structures, particularly the following geometricparameter will be relevant for the properties of the structure. For thewalls, the key parameters are the thickness, the height, the distancebetween the walls, their shape (vertical, straight, curved, circular,sinusoidal, . . . ), their connectedness, and in case of discontinuousstrips, their respective distance. For the support layers, the keyparameters are the distance of the upper and lower support layers; thethickness; and their arrangement (continuous, stripes, . . . ).

In addition to these geometric requirements, the materials used in thewalls and/or support materials can be assessed for their most criticalproperties, namely their “stiffness requirements”, such as can beexpressed by the elastic modulus. Preferred materials exhibit a highelastic modulus, as this allows minimized material usage. Anotherparameter is the elongation at break, which for preferred materialshould be at high values for improved crack resistance, such as duringuse, or during folding. Further, the creep and stress relaxation must below to allow good storage.

As shown in FIG. 1D, in some embodiments, the inner material 122 of theliquid handling member 100 may comprise first and a second supportlayers 202 and 204. The first support layer 202 and the second supportlayer 204 can be arranged in an essentially parallel configurationextending in x-/y-direction perpendicular to their thickness along thez-direction at a distance H to each other. The inner region 120 mayfurther comprise a spacer layer 210 having a material thickness 220significantly smaller than its x-/y extension. The spacer layer 210 canbe arranged and attached in a non-parallel orientation to and betweensaid support layers 202 and 204, whereby the distance H of said supportis greater than the thickness 220 of the spacer layer.

A particularly preferred execution with regard to material compositionrelates to the use of elastomerics for the wall materials, or othermaterials exhibiting a highly elastic behavior. Elastic behavior can beassessed by measuring creep recovery. In this test, the material iscompressed under 8950 Pa (1.3 psi) pressure for i) 2 minutes at roomtemperature , ii) 22 hours at room temperature and iii) 3 days at 60° C.The material is allowed to recover under a 0.23 psi compression pressureat room temperature for 5 minutes. Creep recovery is the recoveredcaliper after long term compression normalized to the recovered caliperafter 2 minute compression at room temperature.

The elastic behavior can be assessed by a simplified creep test asdescribed in the method section, and should result in a creep recoveryafter 22 hrs at RT of not less than 60%, preferably no less than 80%,and more preferably no less than 90%, and most preferably no less than95% or even more than 97%.

Further, the elastic modulus of the materials (also referred to as Youngmodulus) should exceed 5.0 MPa, preferably be more than 10 MPa, and evenmore preferably be even more than 15 MPa.

At the same time, the materials should exhibit a break elongation valueof at least 60%, preferably more than 100%, more preferably more than150%, and most preferably more than 200%.

Preferably, the elastic modulus and the break elongation values shouldbe met after being aged under about 8950 Pa (about 1.3 psi) for at least22 hours at room temperature. Of course, other requirements may beimposed by the intended use conditions, such as safety or comfortconsiderations for the user in certain hygiene applications.

Another preferred execution with regards to material composition relatesto the use of creep resistant, very thin, high modulus materials for thewalls,. These materials need to be thin enough so that when the materialis bent, the local strain along a major portion of the wall is withinelastic limits.

When considering creep resistant elastomeric materials, the followingparticular embodiments have been found suitable:

i) chemically crosslinked rubbers, like isoprene rubber, styrenebutadiene rubber (SBR), and natural rubber; such as produced by AkronRubber Development Labs. (ARDL), Akron, Ohio (PN 36697, isoprene rubber:code ARDL-F, SBR: code SBR, and natural rubber: code DPNR-1A)

ii) chemically/physically crosslinked polyurethanes like roomtemperature vulcanized (RTV) polyurethanes made by mixing prepolymersobtained from BJB Enterprises (Tustin, Calif.).

iii) creep resistant, very thin, high modulus materials in the form offilaments, yarns, ribbons, films, sheets, such as a) liquid crystallinepolymers like i) aromatic polyamides or aramids like Kevlar and Nomex(Du Pont) and Technora (Teijin, Japan), ii) aromatic polyesters likeVectra fibers (Celanese), and iii) aromatic polyimides; b) polyesterswith improved creep properties, e.g. poly-1, 4-cyclohexylene-dimethyleneterephthalate (PCDT, Kodel fibers), c) nylons with improved creepproperties, d) stainless steel, and e) glass fibers.

Generally, suitable support structures should have a low extensibilityso as to maintain the corrugations.

Such support structures can be liquid impermeable, if they do not impedethe liquid handling properties of the structure, for example by notbeing continues, but only nets, open meshes, NW and the like or strips,struts, bands or the like. Alternatively, suitable support structurescan also be liquid permeable, and can have a liquid handlingfunctionality, such as being the membrane materials of liquid handlingmember

Particularly suitable support structures are woven meshes with mono-and/or multi-filament yarns, or apertured films, or non-wovens, ormembrane materials, such as Nylon meshes, as available under thedesignation 03-150/38 from Sefar, Switzerland.

The distance between the support layers may be between 0.05 mm and 30 mmunder no restraining force. The distance between the support layers maybe between 0.05 mm and 30 mm under 8950 Pa (1.3 psi).

The support structure and the wall materials can be bonded to each otherby various conventional ways, such as glues or thermal/heat bonding invarious patterns, though care should be taken, that none of the relevantproperties are unduly affected.

Whilst the above description relates to essentially flat or sheet-likestructures, the same principles apply to three-dimensionally shapedstructures, which—for example—can be constructed by combining two ormore of these structures on top of each other. Thereby, the designprinciples remain unchanged, whereby the wall materials of two differentlevels can have one and the same support sheet, i.e. one being attachedto one side of the support sheet, and the other to the opposite side.

Such two- or multi layer structures can further have the sameconstruction, or can have different properties in different levels. Sucha structure also can have the same x-and/or y-extension for allsub-layers, and thus create a “macro-layer” or the sub-layers can havedifferent extensions, such that a irregularly shaped volume for themember can result.

Depending on the intended application, it may be particularly desirablefor the combined structure (i.e. support and wall elements combined) toexhibit certain deformation properties. In particular, in addition tothe compressibility requirements for the structure (which essentially isalong the thickness direction of the structure), the flexibility anddeformability in x- and in y-direction can be of importance. For certainapplications, the structure should be very flxible and deformable, suchas when used in otherwise pliable or flexible articles, in particularwhen being used in hygine articles. For other applications, thedeformability should not be too high, or the respective flexibility toolow, so as to provide a certain structural integrity to the otherwisestill deformable structure.

For hygiene applications, such a external catheter, or absorbentarticles like disposable diapers the resulting structure shouldgenerally be quite deformable and pliable to comply with the bodycontours of the wearer, and/or to comply to change of the body contoursduring use, such as by movements or change of position. Suchdeformability and softness provides increased comfort during wear. As iswell known softness is a subjective, multi-faceted property includingcomponents such as bending resistance, buckling resistance andcoefficient of friction. As is also known the tensile properties of amaterial are also important as a predictor of softness. In particular,materials having a low tensile modulus and high elongation aredesirable. However, as also well known from corrugated cardboards, thebending in x- or y-direction (i.e perpendicular to the thicknessdirection) can be impacted by the three.

Such deformability can be assessed by considering bending and bucklingresistance. An especially desirable measure of the bending component ofsoftness in the case of absorbent article core components has been foundto be buckling resistance. As will be recognized by one of skill in theart, the corrugated structure as described in the above can assume anarcuate configuration such as when implemented into an absorbentarticle, and applied to the wearer, where it should conform to awearer's anatomy. The Bulk Softness test described in the Test Methodssection below uses resistance to compressive deformation of a samplehaving a controlled arcuate configuration as a measure of the softnessof the sample. Suitably, a structure according to the present inventionhas a buckling force of less than about 10 N. Preferably, the bucklingforce is less than about 5 N, more preferably less than 3 N or even lessthan about 1 N.

In a particular embodiment, the ratio of the buckling force inx-direction to the buckling force in y-direction is more than 0.7 andless than 1.3.

When considering a preferred application of the present invention,namely the use of liquid handling members in hygiene articles, the usedmaterials preferably are non irritating, or allergenic. Further, forsuch applications, the expected loading conditions for the article canbe estimated, which can be total loads of 400 ml or more, delivered ingushes of 75 ml or more, with gush rates of 15 ml/sec or more. In orderto allow liquid handling members to cope with such requirements, asample structure can be constructed as follows:

A sheet of elastomeric of the type as described in the above (ARDL code:SBR, PN 36697) having a caliper of about 0.4 mm a Young modulus of about7 Mpa; and a break elongation of about 100%), is prepared by beingscissored into a 15 cm×14 cm piece. Its total weight and caliper aredetermined at various locations to allow meaningful averaging. The pieceis cut into stripes of about 3 mm width. Two 5 cm×15 cm pieces of thenylon support 150 micron nylon mesh (03-150/38 from Sefar, Switzerland)and the respective weight and caliper are determined. Using rods ofsuitable size and material, such as Perspex or steel or wood, theelastomeric stripes are corrugated and the ends are fixed to a suitablesupport surface (e.g. benchtop) with tapes. Also, use tapes to keep therods in place. Suitable corrugated structures were made using rodsranging in diameter from ⅛″ to 5/16″. For discontinuous corrugations,adjacent rubber corrugations are placed on the mesh spaced apart, suchas having a gap of 9 mm between the stripes.

A thin layer of suitable adhesive, such as a cyanoacrylate adhesivecommercially available under the trade designation “Super Jet Glue”(Carl Goldman Models, Chicago, USA), is put on the crests of thecorrugation loops, thus bonding it to the nylon mesh.

Then, a conventional polyethylene film is put on top of the nylon meshand a pressure of about 8950 Pa (about 1.3 psi) is applied for about 5minutes. The weights and the films are removed, and the structure isallowed to air dry for about 1-3 hours under the controlled labconditions.

Then, the structure is flipped over and the second support structure inform of a same nylon mesh is attached to the other side in the same way.Excess elastomer is trimmed off, and the weight and caliper of the innermaterial is measured.

The resulting structure has a structure height of about 6 mm, with about1 repeating unit per cm, whereby the corrugated elements cover about 25to 50% of the total area..

Test Procedures

Unless otherwise noted, the tests are carried out under standardlaboratory conditions of 22° C. and 50% relative humidity, withdistilled or deionized water as test liquid.

Caliper

Caliper is measured by an caliper gauge such as Ono Sokki gauge modelno. EG-225 (0.001˜25 mm), Ono Sokki, Japan , having a foot diameter of1″ and foot weight of 40 g.

Caliper is measured at 0.23 psi and 1.3 psi compression pressures. Thesecompression pressures are applied by placing appropriate weightsdirectly on the sample and then measuring the total caliper of thesample and the weights. This protocol was necessary for the followingreason. When the corrugated structure collapses, there is shear betweenthe top and bottom support plates. Hence, any measure of caliper underpressure had to provide for the plates to slide horizontally.The following weights were used to get the appropriate compressionpressure (2 cm×4.5 cm sample):⅛″ Lexan plate: 36.9 g, 3.3 mm×10 cm×10 cm⅜″ Lexan plate: 69.7 g, 9.1 mm×8.3 cm×8.3 cm⅜″ SS plate: 776 g, 9.5 mm×10 cm×10 cmGauge foot: 40 g0.23 psi: ⅛″ Lexan+⅜″ Lexan+gauge foot1.3 psi: ⅛″ Lexan+⅜″ SS+gauge foot.Creep Recovery

This tests aims at determining the resistance to permanent deformationunder an external load, whereby the load is applied in the direction aswould correspond to in-use conditions.

A sample is prepared by cutting a 2 cm wide and 4.5 cm long piece out ofthe material.

A weight is prepared to create 9080 Pa (1.3 psi) pressure such as byusing 10 cm×10 cm×⅜″ stainless steel plate covered 10 cm×10 cm×⅛″ LEXANlayer on the material oriented side, the plate and the LEXAN weighing853 g. The weight is placed onto the upper surface of the test material,and allowed to compress the material for 2 minutes, in further test runswith further samples for 30 minutes, and 22 hrs at standard roomconditions of 25° C. temperature and 50% RH. A fourth test specimen canbe tested for 3 days at 60° C.

Upon removal of the weight at the end of the compression period, therecovered caliper is measured by an caliper gauge such as describedabove as a function of time for 5 minutes.

The creep is expressed in percent of recovery normalized by the recoveryafter 2 minutes load.

Minimum Liquid Loading

This is the amount of liquid in a liquid handling member at the pointwhere the member looses it functionality, when liquid is sucked out ofthe member.

In order to measure this value for an inner material, a sample of 5 cmby 15 cm at the uncompressed thickness of the inner material ishermetically sealed in a suitable membrane material such as the type03/10-5 or 03/20-14 of Sefar, Switzerland.. The weight of the innermaterial as well as of the composite is recorded as “dry weight”.

This composite is saturated under free swell conditions with water atroom temperature, by immersing it therein, whilst allowing air to escapevia at least one corner which is kept dry until all the remainder isfilled. The weight of the composite is recorded as “saturated weight”.

The composite is placed on a stack of 20 sheets of filter paper of about10 cm by 10 cm (4″ by 4″)(such as Whatman Type 989 under a compressionload of 413 Pa (0.06 psi), such that water is desorbed until air issucked through the membrane. If the desorption paper is too highlyloaded, it can be replaced by fresh filter paper. This desorption can beaided by first squeezing out a part of the liquid between two platessuch as 20 cm by 20 cm Perspex or Lexan plates, which can be manuallycompressed, carefully avoiding localized pressurizing, and too highpressure.

As soon as the first air bubble enters into the system, the composite isremoved from the desorption paper, and the weight as is recorded as“minimum liquid loading weight”.

The “minimum liquid loading” of the inner test sample is the leastamount of liquid remaining in a compressed material expressed in theunits of grams of liquid per gram of dry material..

Surge Capacity

The surge capacity of an inner material or member describes the amountof liquid which a member can receive, whereby this material or member ispre-loaded to a certain extent and prefilled and compressed to a certaindegree. The test can be executed in two ways, namely when the sample isbeing positioned either essentially horizontally flat, or vertically.

For both approaches, an inner material—after determining its “dryweight”—is hermetically sealed into a suitable membrane, such as theSefar material as described above.

The composite is saturated with liquid as above. Then, this composite iscompressed either manually or by suitable tools such as automaticpresses, or by being dried by suitable suction means such as the abovedescribed filter paper, until a certain amount of liquid remains therein(the “initial liquid loading” which needs to be higher (about 0.2 to 0.5g/g ) than the above referred to “minimum liquid loading”). Thecorresponding weight is recorded.

The composite is then wrapped into a liquid impermeable, flexible film,such as conventional PE (Saran) film or bag or aluminum foil, and storedin the compressed state for 5 minutes.

Both tests can be repeated several times, as the surge capacity ofsuitable materials does not substantially change over multiple gushes.

Horizontal Surge Capacity

The compressed, unwrapped composite is placed on a suitable plate, suchas made form Lexan or perspex, which is arranged at a 5° angle to thehorizontal, and a load is applied corresponding to 1580 Pa (0.23 psi) bymeans of a further LEXAN plate and stainless steel plates. Liquid isdelivered to the composite, such as by using a 50 ml pipette at a ratesufficiently slow to allow to be picked up until its saturation, whichis recorded upon visual observation of liquid overflow. The composite isre-weighed, after surplus liquid has been removed (i.e. the overflow orother non-absorbed liquid). The Horizontal Surge Capacity is calculatedfrom the amount of liquid picked up divided by the weight of the dryinner material, expressed in g/g (i.e. g liquid/per gram of dry innermaterial).

Vertical Surge Capacity

The compressed, unwrapped composite is immersed into a reservoir of testliquid, whereby the reservoir is placed on a scale, and the composite ishung from a separate support structure, being immersed into thereservoir by 5 mm.The weight change of the reservoir is recorded for 3minutes, at least initially at least every 5 seconds. After 3 minutes,or 20 seconds respectively, the sample is removed from the reservoir,and reweighed to determine the Vertical Surge load.

The Vertical Surge Capacity is calculated from the liquid pick updivided by the dry weight of the inner material, and expressed in g/g.

Volume Expansion Factor

The Volume expansion factor is defined by the relative expansion of theinner material which corresponds to the liquid uptake in the above surgecapacity tests. For aqueous liquids such as synthetic urine with adensity of about 1.0 g/cm³, the volume expansion factor corresponds tothe gravimetric expansion factor.

Hence, for such systems, the volume expansion factor can be calculatedby dividing the g/g liquid loading in the expanded state (afterhorizontal or vertical surge tests) by the g/g liquid loading in thecompressed state (i.e. initial liquid loading

Bulk Softness

This method is intended to measure individual materials as well asstructures comprising these materials. The method uses a tensile testerin compressive mode and a sample holder (FIG. 2) to measure the bucklingforce for a sample.

A suitable tensile tester is available from Zwick Company of Ulm,Germany as a Zwick Material Tester type 144560.

The sample holder 1010 for this test is shown in FIG. 2. As can be seentherein the sample is held between two curvilinear plates 1020 that havetabs (1030, 1032) 30 mm wide that extend upward 20 mm (front element,1030) and 55 mm (rear element, 1032) so as to enable insertion of thesample holder 1010 into the jaws of the tensile tester. Readily thecurvature of the outer element 1014 of the holder has a radius of 59mm±1 mm with an arc length of 150 mm and the inner element 1016 has aradius of 54 mm±1 mm with an arc length of 140 mm. The equipment isdesigned to test various material thicknesses from 1 mm up to 10 mm. Aswill be recognized, sample holders of this type are necessary for boththe upper and lower jaws of the tensile tester.

Prior to testing a sample is conditioned under controlled conditions(50% RH, 25° C.) for at least two hours. The sample is cut to 60 mm×150mm (±2 mm per dimension). The sample dimensions, short side vs. longside, should be consistent with the bending axis orientation for whichthe test is executed, and can be aligned with the intended use in afinished product, whereby the y-axis generally corresponds to theleft-right orientatin of the user, and generally to the width dimensinof the article, and the x-axis being perpendicular thereto. Theoperation is as follows:

-   1. The tensile tester is calibrated (in compressive mode) according    to the manufacturer's instructions.-   2. The compression rate is set to 200 mm/minute and the crosshead    stop point to 30 mm.-   3. A sample is inserted into the sample holder to a depth of 7 mm ±1    mm for each clamp set.-   4. The tensile tester jaw separation is set so that the    unconstrained portion of the sample is smooth and unbuckled. This    corresponds to a spacing between the upper and lower portions of the    sample holder of 46 mm.-   5. The sample/sample holder assembly is inserted into the jaws of    the tensile tester.-   6. The tensile tester is operated in compressive mode to record a    force/compression curve for each sample.-   7. The buckling force for each sample is recorded, which is the    force required to cause the sample to initially begin to bend. It is    the initial peak force that is seen on the force compression curve    before a relatively constant force plateau that is a measure of the    bending resistance of the sample (bending force) and is expressed in    Newton (N).-   8. Repeat steps 5 to 7 for at least 5 samples for each structure    tested and report the average and standard deviation of the buckling    forc    Compression Set Test

This test is executed by following the instructions according to ASTMD-395-97 *(Standard Test Method for Rubber Property—Compression Set,Method B, with a compression time of 22 hours under a temperature of 60°C.

1. A deformable liquid handling member having a inner regioncircumscribed and hermetically sealed by a wall region, said wall regioncomprising a membrane assembly to separate a first zone outside of themember from a second zone within the inner region of the member, whereinsaid second zone is in fluid communication with a suction source capableof receiving liquid, and said first zone is positioned in liquidcommunication with a liquid releasing source during its intended use,wherein said membrane assembly is capable of maintaining a pressuredifferential between the second zone and the first zone withoutpermitting air to penetrate from said first zone to said second zone,wherein said inner region comprises an inner material, wherein the innermaterial is an elastomeric material, said inner material having a volumeexpansion factor of more than 3; wherein said inner material comprises afirst support layer and a second support layer, arranged in anessentially parallel configuration extending in x-/y-directionperpendicular to their thickness along the z-direction at a distance Hto each other, and a spacer layer having a material thickness bsignificantly smaller than its x-/y extension, said spacer layer beingarranged and attached in a non-parallel orientation to and between saidsupport layers, and whereby the distance H of said support is greaterthan the thickness b of said spacer layer.
 2. A deformable liquidhandling member according to claim 1, wherein said inner material has acreep recovery of more than 60%.
 3. Liquid handling member according toclaim 1, wherein said inner material has a net uptake value of more than6.5 g/g in the horizontal Surge Capacity test.
 4. Liquid handling memberaccording to claim 1, wherein said inner material has an net uptakevalue of more than 5.5 g/g in the vertical Surge Capacity test. 5.Liquid handling member according to claim 1, wherein said inner materialexhibits said values after accelerated aging for 3 days at 60° C. 6.Liquid handling member according to claim 1 wherein the distance betweensaid support layers is between 0.05 mm and 30 mm under no restrainingforce.
 7. Liquid handling member according to claim 1 wherein thedistance between said support layers is between 0.05 mm and 30 mm under8950 Pa (1.3 psi).
 8. Liquid handling member according to claim 1wherein said inner material comprises a spacer layer arranged incorrugations, pleats, folds, walls, tubes, spheres, and semispheres. 9.Liquid handling member according to claim 8, wherein said corrugationsare discontinuous.
 10. Liquid handling member according to claim 1,wherein said spacer layer comprises material selected from the group ofvulcanized polyurethane, and chemically cross-linked rubber.
 11. Liquidhandling member according to claim 1, wherein said support layercomprises creep resistant fibers.
 12. Liquid handling member accordingto claim 1, wherein said spacer layer comprises creep resistant, thin,high modulus material.
 13. Liquid handling member according to claim 1,wherein said support layer comprises elastomeric material.
 14. A liquidhandling member according to claim 1, comprising a multiplicity ofspacer layers and support layers.
 15. Liquid handling member accordingto claim 1, wherein said member exhibits a buckling force of less then10 N, in at least one of the x- or- y-direction oriented perpendicularlyto the thickness direction of the member, when submitted to the bulksoftness test.
 16. Liquid handling member according to claim 15, whereinthe ratio of the buckling force in x-direction to the buckling force iny-direction is more than 0.7 and less than 1.3.
 17. A deformable liquidhandling member having an inner region circumscribed and hermeticallysealed by a wall region, said wall region comprising a membrane assemblyto separate a first zone outside of the member from a second zone withinthe inner region of the member, wherein the inner region comprises aninner material selected from the group consisting of chemicallycrosslinked rubbers, chemically crosslinked polyurethanes, physicallycrosslinked polyurethanes, and creep resistant high modulus materials;wherein said second zone is in fluid communication with a suction sourcecapable of receiving liquid, and said first zone is positioned in liquidcommunication with a liquid releasing source during its intended use;wherein said membrane assembly is capable of maintaining a pressuredifferential between the second zone and the first zone withoutpermitting air to penetrate from said first zone to said second zone;wherein said inner material comprises a first support layer and a secondsupport layer, arranged in an essentially parallel configurationextending in x-/y-direction perpendicular to their thickness along thez-direction at a distance H to each other, and a spacer layer having amaterial thickness b significantly smaller than its x-/y extension, saidspacer layer being arranged and attached in a non-parallel orientationto and between said support layers, and whereby the distance H of saidsupport is greater than the thickness b of said spacer layer.